Cleaning of optical surfaces

Written by 杨 道波 Monday, 01 November 2010 14:53

The photographer alerted takes great care of optical equipment as it is known that dust, dirt of all kinds, and microrays scratches on the surface of the lenses and filters, violations of anti-reflective layers, inevitably affect image quality. The best thing is ... not dirty.

When should you clean? As might have told Mr. La Palisse when the lens is dirty! What is certain is that a few scattered dust will have little effect on image quality while too frequent interventions will eventually cause considerable damage optical surfaces.

This picture does not lack charm, but we note oblique streaks due to directional diffusion of light from bright light sources located in the field. It is likely that the target has been poorly cleaned after being contaminated or that it bears many micro scratches from wiping aggressive.

Preventive Measures

* Always store equipment in a clean, dry, outside periods of use.
* Leave the plugs of goals if you do not need the camera is constantly ready to serve.
* Outside of cases where the risks are too great, a visor adapted to the objective provides good protection against both flare and cons shocks. However, the risks increase when the focal length decreases as the angle of the sun visor is then greater than in the case of long focal length objectives. It also does harping enough that the presence of a sun visor effectively contributes in every conceivable situation, obtaining photographs of the highest quality possible.
* Protect the front lenses of objectives. The establishment of a permanent UV filter, especially if it is not accompanied by that of a sun visor, alters the image sharpness and reduces its contrast due to internal reflections. It must in any case the filter is high quality and undyed (absolutely proscribe the filters "Skylight" that give shades of pink or yellow images). The presence of a UV filter is really desirable that if the lens is exposed to salt spray, to projections of sludge to clean or dusty atmospheres, etc.. In this case cleaning the front of the filter will of course be less dangerous than the front lens.
* Between uses, if the atmosphere is humid, it's good to lock the camera in a waterproof bag or box containing a sufficient quantity of absorbent material such as "silica gel", which will reduce the risk of corrosion or attack by fungi.

Cleaning equipment

Blower brush and cleaning fluid

Found in the photographic trade and opticians various products designed for cleaning optical surfaces. They are mostly effective but their use should not be indiscriminate. Manufacturers of precision optical equipment unanimously recommend the following equipment:
7 in 1 Lens Cleaning Kit for Canon Nikon Pentax Sony

* From the clean, dry and lint-free.
* A blower, ideally a nozzle delivering dry nitrogen. Bombs blowing agree but they should be used with caution and clear of all items to clean. Pears blowers, especially if they involve a brush, must be kept very clean so as not to redeposit the dust as and cleaning.
* Distilled water (not distilled)
* From mild soap, and acid or alkaline above, fragrance and dye, diluted to 1% in pure water and can apply for "green soap" to his favorite pharmacist, we dilute a few drops in a glass of water.
* From the isopropyl alcohol and acetone high degree of purity products for spectroscopy are recommended.
* Cotton swabs. Beware of plastic sticks that could be dissolved in solvents.
* Eventually, laboratory gloves made of polyethylene for cases where cleaning requires immersion. Latex gloves are not suitable on the one hand they are attacked by acetone and secondly they are kept in the talcum powder that you would not fail to find on the surfaces.

Dust removal

Debris of all kinds can be deposited on optical surfaces and adhere very strongly, driven by electrostatic charges or other processes. Operate in three phases:

* Blow dust: generally any large particles are easily removed, but it is often the smaller ones, fat ones, etc..
* Wrap a cloth around a very clean cotton swab, moisten all alcohol and very gently wipe the surface clean. It is recommended that traverse the surface in a given direction by making movements in the form of "loops" (referring to the mountain roads). This operation usually leaves traces on the glass.
* Renew the cloth and cotton swab and repeat.
* Repeat the previous step with acetone this time to remove the last traces.

Removal of Fingerprints

Should be eliminated because the emergency substances deposited by the skin attacking the glass and coatings. The direct and exclusive use of a solvent has the effect of spreading the contamination, which ultimately does not help. Be careful when cleaning the filters made of gelatin mounted under glass, it should in no case the wet edge, even if it is protected by a varnish.

* Blow dust.
* Wrap a cloth around a very clean cotton swab, moisten the whole of a soap solution, wipe the surface as has been said before.
* Repeat this process.
* Repeat with alcohol.
* Repeat with acetone.

Cleaning the optical fragile

Some optical elements such as mirrors that reflect light from the front with a metal surface, the object must be more attentive care. Their cleaning should be undertaken only if we really can not do otherwise, and it is particularly delicate. Rather than doing it yourself, if you do not have the necessary equipment, it is best done by a specialist. It must above all avoid any friction surfaces, which are extremely fragile, and proceed with the removal of dirt just by shaking. Do not use the method described below for the bonded or containing plastic parts, because they might not resist solvents.

* Blow dust.
* Prepare four plates each containing soapy water, distilled water, isopropyl alcohol and acetone. Place the bottom of each box disc tissue to prevent damage resulting from accidental contact.
* Soak the item in the soapy solution, shake gently for at least one minute, then remove it and let it drain a few seconds.
* Repeat this process in distilled water.
* Repeat in isopropyl alcohol.
* Repeat finally in acetone.
* Dry blowing.

What you should never do!

* Rub an optical surface before removing the dust: this would lead inevitably microrays formation and degradation of surface coatings.
* Blow a bomb too close to the lens: the sudden cooling that would result is likely to shatter glass.
* Reuse several times a dose of solvent is the best way to redeposit dirt.
* Use paper towels for household use: they almost always contain abrasive particles are very harmful to surfaces.
* Reuse paper or tissues that have been used: they are loaded with abrasive dust and certainly produce scratches. However, there are washable fabrics, which must obviously be kept very clean.
* Use a "chamois" is an excellent dust catchers and repeated use quickly produce the same effect as sandpaper.
* Handle alcohol and acetone near a flame or heat source, these products are highly flammable!

Related articls :
Last Updated on Monday, 01 November 2010 15:20